Could try charming the guards, depending on their preference depends if Charity or one of your guys would be best ;)

That could always be the "obvious" ploy, which they know won't work and that the guard will become suspitious, so they also do a feint to get in through a way they know they'd get caught, leaving 2 of them to actually hit the real target whilst the other 2 are being "told off/having their wrists slapped." If they get caught, that was only the decoy plan. If they don't and the person who is hitting the ploy exit might just get in. Either way, they cover their bases and get what they want.

Just a thought, not original but might work.